The present invention relates to apparatus for detecting defects in a semiconductor device and, more particularly, to apparatus for detecting electrical defects in a semiconductor device and methods for using the same.
During the manufacture of semiconductor devices, various defects can occur. These defects may cause malfunctions and failures in the semiconductor devices. The defects introduced during manufacture of the devices can generally be divided into two categories including physical defects, such as particles, which cause a physical abnormality on the surface of a semiconductor substrate and electrical defects which do not accompany physical defects but bring about electrical failure in a semiconductor device. Physical defects can generally be detected by conventional image observation equipment. However, electrical defects cannot typically be detected by ordinary surface detection equipments.
It is known to test contact holes extending to a doped region of a semiconductor between the spacers along the walls of the stacked structure of a formed gate electrode using an electron beam inspection apparatus. In-line monitoring of whether a contact hole formed in the semiconductor substrate is in an open or not-open state is performed using the electron beam inspection apparatus. If an unetched material layer (e.g., an oxide or nitride layer) is present in the contact hole, primary electrons may not flow properly to the silicon substrate so that electrons accumulate on the surface of the unetched material layer. Then, a large amount of secondary electrons may be emitted from the surface of the silicon substrate. Depending on a difference in secondary electron yields, a brighter (white) or darker (black) image may be displayed for a portion where a large amount of secondary electrons are emitted, that is, a portion where the unetched material layer is present, compared to portions where the unetched material layer is not present. However, such an approach may not reliably detect all unetched conditions and further is performed before material is deposited in the contact hole.
Accordingly, it would be desirable to provide improved methods and apparatus for the detection of electrical defects during the manufacture of semiconductor devices.
Methods and apparatus for detecting defects in a semiconductor device including a plurality of conductive pads are provided in accordance with various embodiments of the present invention. The methods include accumulating electrons in ones of the plurality of conductive pads and detecting a first contrast between the ones of the plurality of conductive pads based on secondary electron emissions from the ones of the plurality of conductive pads after electrons are accumulated in the ones of the plurality of conductive pads. Holes are accumulated in the ones of the plurality of conductive pads and a second contrast is detected between the ones of the plurality of conductive pads based on secondary electron emissions from the ones of the plurality of conductive pads after holes are accumulated in the ones of the plurality of conductive pads. It is determined whether a defect is present in one of the conductive pads based on the first contrast and the second contrast.
In other embodiments of the present invention, the detecting operations include applying a primary electron beam to the ones of the plurality of conductive pads. The accumulating electrons and holes may be accumulated at a surface of the ones of the plurality of conductive pads. Electrons may be accumulated by adjusting the energy of a primary electron beam applied to the ones of the plurality of contact pads to a first level and holes may be accumulated by adjusting the energy of a primary electron beam applied to the ones of the plurality of conductive pads to a second level. The electrons and/or holes may, alternatively, be accumulated using an ion generator.
In further embodiments of the present invention, a first voltage contrast associated with the one of the conductive pads is detected and a second voltage contrast associated with the one of the conductive pads are detected. Detecting operations may further include associating either a first bright image or a first dark image with the one of the conductive pads based on the detected first voltage contrast and associating either a second bright image or a second dark image with the one of the conductive pads based on the detected second voltage contrast. The voltage contrast may be determined based on a standard value. Alternatively, the voltage contrast may be determined based on a comparison of secondary electron emissions from the one of the conductive pads and secondary electron emissions from at least one other one of ones of the plurality of conductive pads.
In other embodiments of the present invention, determining whether defects are present may include determining that an electrical defect caused by a junction leakage source is present in the one of the conductive pads when the one of the conductive pads is associated with a first dark image and a second bright image. It may also be determined that an electrical defect caused by a non-etched contact portion between the one of the contact pads and a semiconductor substrate of the semiconductor device is present in the one of the conductive pads when the one of the conductive pads is associated with a first bright image and a second dark image. It may further be determined that an electrical defect caused by a short-circuit between the one of the conductive pads and an adjacent conductive line of the semiconductor device is present in the one of the conductive pads when the one of the conductive pads is associated with a first bright image and a second bright image. It may also be determined that a physical defect is present in the one of the conductive pads when the one of the conductive pads is associated with a first dark image and a second dark image.
In further embodiments of the present invention, the electrons are accumulated by generating a voltage difference between a surface of the semiconductor device and a backside of the semiconductor device selected to provide an accumulation of electrons in the ones of the conductive pads. The holes may be accumulated by generating a voltage difference between a surface of the semiconductor device and a backside of the semiconductor device selected to provide an accumulation of holes in the ones of the conductive pads. The voltage difference may be generated by adjusting the energy of a primary electron beam applied to the ones of the plurality of conductive pads.
In other embodiments of the present invention, apparatus are provided for detecting defects in a semiconductor device including a plurality of conductive pads. The apparatus include an electron beam source configured to apply a primary electron beam to the semiconductor device having a first state which causes accumulation of electrons in ones of the plurality of conductive pads, a second state which causes accumulation of holes in the ones of the conductive pads, and a third state that allows detection of secondary electron emissions from the ones of the plurality of conductive pads. The apparatus further include a data analyzer configured to detect a first contrast between the ones of the plurality of conductive pads based on secondary electron emissions from the ones of the plurality of conductive pads after electrons are accumulated in the ones of the plurality of conductive pads and to detect a second contrast between the ones of the plurality of conductive pads based on secondary electron emissions from the ones of the plurality of conductive pads after holes are accumulated in the ones of the plurality of conductive pads. The data analyzer is further configured to determine whether a defect is present in one of the conductive pads based on the first contrast and the second contrast. The apparatus may also include a stage control unit configured to detect positions on the semiconductor device of defects determined to be present.